how do you figure bed size

[Sherill Colgin]

How do you figure bed size if you are using 6 inch 10 ft pc of pvc with 10 holes for net pots? Is it the size of the amt of medium or the are of the bed or what?

[TCLynx]

When doing NFT in pipes, figuring the bed size doesn't really do much for you since you get very little filtration from the NFT pipes.

 

You will need some sort of filter to take care of bio-filtration and solids filtration before you send your water to your pipes or you will have problems with gunk building up in the pipes and causing a stinking mess and stunting your plants.

[Sherill Colgin]

How would the plants get nutrient from the fish if you add a solid filtration system. I lost all my fish when a system failure caused the water in the backyard fish pond to empty. I am trying to fishless recycle before adding more fish. I have a grow bed that is 2ft x 4 ft approx. 6 inches deep with many plants. The medium is hydroton. Maybe I should redesign and have the water go into the flood and drain bed before going into the pvc pipe? I can't do that until the end of the season because the bed whould have to be higher than the pvc pipe. What do you think?

[TCLynx]

The plants get the nutrient that is in solution in the water.  If your solids and fish water go into some form of filtration and the bacteria do the conversions in the filter and the water that comes out has the nutrient in it.

 

Yes I think a media filled grow bed is a great way to filter water before sending it to you NFT pipes.  There is an option that you could set up a small sump tank below your grow bed and have the water drain from the grow bed into that "clean water sump" and have a small pump in there to feed your NFT pipes which is an option if raising you bed or lowering the nft won't work well.  You would probably need an overflow from the "clean water sump" back to the main fish tank in case your NFT pump was too small to keep up and of course you would need to make sure the "clean water sump" had enough water or enough flow into it to keep up with the small NFT pump so it didn't run dry.

 

Hope this helps.

[Sheri Schmeckpeper]

Dr. Wilson Lennard created an Excel spreadsheet that calculates tank vs fish vs media size. (attached) The companion PDF file explains it. It's an interesting model, but quite complex. So much of the balance is trial and error because we all have different water, varying sized fish, are using different methods and provide different environments for our systems. Also, different plants consume differently. But if you're into the detail and measurements, this might give you something to work with. :)

As for us, our 200 gal tank is feeding about 32sf of bed plus 16sf of water lettuce, which consumes nitrates and provides shade. I'm not sure how much further we can go, but we'll keep expanding until the plants protest!

BTW, I like your first name. It's rarely spelled Sherill, which is my given name. :)

[TCLynx]

I've found that with a media bed system, it works out pretty well to have between equal media bed volume to fish tank up to about twice as much media bed volume as fish tank.  This works pretty well for making sure there is plenty of filtration and solids handling capacity for a backyard scale system.  Now when you start adding in rafts and NFT no one really knows yet how the systems will handle the solids long term but it all varies from system to system anyway since in one climate the worms might make quicker work of the solids than in another location.

[Sheri Schmeckpeper]

You need something to start the cycling, so if you don't have fish you may need some chicken manure or other ammonia-producer. Then the bacteria in your system will kick in and create the nitrates for your plants. The nutrients are in the water, so filtering solids is simply to keep things flowing smoothly.

We have a flood & drain system, but will be adding some floating beds. It all works on the same principles, though. You have to have ammonia producers and you have to have bacteria and a place for it to grow.

We have a separate bio filter that our water flows through, with lava rock and filter media. That way if anything happens to our hydroton grow bed, we still have bacteria in the system, and if anything happens to our filter, the bacteria is still in the hydroton. We also keep some rocks in the bottom of our tank. That gives at least three good places for the bacteria to grow. I've worked in technology long enough to know that a backup is essential, and two backups are that much better.

:)

[TCLynx]

I don't personally recommend chicken manure as an ammonia source in an aquaponics system.  There are pathogens that can pass between chickens and people and any warm blooded animal manure should be properly composted or steps taken to make sure all possible pathogens are killed before use in an aquaponics system where people might eat uncooked veggies from it.